1. Field of the Invention
The present invention relates to an optical coherence tomography apparatus. More particularly, the present invention relates to an optical coherence tomography apparatus for displaying a tomographic image.
2. Description of the Related Art
In recent years, optical coherence tomography apparatuses using a principle of optical coherence tomography (OCT) in which multi-wavelength interference is employed have been increasingly applied to the diagnosis of human bodies. For example, the OCT apparatuses have become to be applied to endoscopes to acquire information about internal organs or to ophthalmologic apparatuses to acquire information about retinas. The optical coherence tomography apparatuses applied for the diagnosis of eyes have become essential as the ophthalmologic apparatuses in outpatient clinics specialized in retina care. The OCT apparatuses irradiate a sample with a measuring beam, which is low coherent light, so that the OCT apparatuses can measure back scattering light from the sample with an interference system. When the OCT apparatuses are applied to the diagnosis of eyes, the apparatus can capture tomographic images of a subject eye at a high resolution by scanning the subject eye with the measuring beam. Using the advantage, the apparatuses are widely used for ophthalmic diagnosis for retinas, and the like.
However, in the OCT apparatus, speckle noise is produced by interference of scattering light due to a structure of a measurement target. Further noise depending on the sensitivity of a detector (a line sensor or a photo diode) may be produced due to reduction of the light amount for reducing a load. To solve the problems, Japanese Patent Application Laid-Open No. 2010-110392 discusses a technique for increasing image quality of tomographic images by scanning the same part of a subject eye a plurality of times, aligning the tomographic images captured by the scanning, and averaging the values.
Further, Japanese Patent Application Laid-Open No. 2008-237238 discusses an optical coherence tomography apparatus for increasing image quality of tomographic images by aligning a plurality of adjacent tomographic images and combining the images. As described above, to obtain high-quality tomographic images in the optical coherence tomography apparatuses, the processing for reducing the noise, for example, by aligning the plurality of acquired tomographic images and combining the images, is important.
However, in the above-mentioned optical coherence tomography apparatuses, the tomographic image is displayed after the alignment and combination of the plurality of tomographic images. As a result, the examiner cannot see the tomographic image until the alignment and combination processing is completed. Consequently, it is difficult to determine whether the image has been successfully captured right after the image capturing.
Meanwhile, when a subject eye is scanned and images of the subject eye are captured, the same part of the subject eye is scanned a plurality of times, and the acquired tomographic images are added to reduce speckle noise, random noise, and the like. In another method, the imaging regions of the subject eye are moved to capture tomographic images. Further in another method, the same part is scanned a plurality of times and the imaging regions of the subject eye are moved to capture tomographic images. However, by the above-mentioned image capturing methods, it is not possible to change the image for checking whether the image capturing has been successfully performed.